Sharpness of movement is observed in Involutionary types, along with sporadic shifting from one activity to another. These sudden shifts overtly contrast to the smoothness of Evolutionary types. In traditional Socionics, sharp movements are attributed to Rationality. In my opinion, however, this quality is more determined by Involution. For counterexample, consider the Evolutionary Rational types LSI and EII, whose motions are characteristically soft and smooth. Yet the nature of movement in Involutionary Irrationals SLE and IEE is so sharp that training them smooth movement is practically impossible.